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W. `O. HOTCHKISS ET AL Feb. 19, 1929.

PHYS I CAL I NSTRUMENT Filed June 27, 1927 4 snexs-sn'eet 1 H. TEAR/V.

/4 JOHN Fofpsr.

Febfl, 1929.

W. `O. HOTCHKISS El' AL PHYS I CAL INSTRUHENT Filed June 2v. 1927 4'sneeis-sneet 2 Feb. 19, 1929.

W. O. HOTCHKISS ET AL PHYS I CAL I NSTRUMENT Filed June 27. 192'? 4 Sheefos-5heet Feb. 19, 1929.

W. O. HOTCHKI'SS ET AL PHYS ICAL I NSTRUMEN T Filed June 27. .1927 4 Sheets-Sheet 4 ou Q0 Patented Feb. 19, 19249.

UNITED. STATES PATENT oFFicE.

WILLIAM O. I-IOTCHVKISS, OF HOUGHTON, MICHIGAN, HENRY R. ALDRICH, 0F MADISON, i, WISCONSIN, NOEL H. STEARN, OF ST. LOUIS, MISSOURI, AND JOI-IN I?. FOERST, OF MADISON, WISCONSIN, ASSIGNORS TO W. C. MCBRIDE, INC., F ST. LOUIS, MISSOURI,

A CORPORATION OFVDELAWARE.

PHYSICAL INSTRUMENT.

Application filed June 27,

, This invention relates generally to physical instruments, and more specifically to an improved instrument resembling the dip needlc, the predominant object of the invention being te produce instruments of this general type which are practicablefand which, being much mere sensitive than the ldip needles heretofore known, will serveV to enlarge the known field of application, and also open up new fields; that is, an instrument which will p detect and measure the comparative magni tude of very slight changes in intensity or inclination both from time to time and from place to place in the earths magnetic field defined here as the total resultant of the normal field either unmodified or modified 'l either by natural or human agency Vwhether controllable or uncontrollable or by any combination thereof.

The primary object of the instrument is to assist in locating deposits of all types of natural resources including oil, coal, non-metallic, and metallic minerals, as well as all materials or bodies natural or artificial which pro duce directly or indirectly changes in the earths normal field. The relationship bef tween natural resources and variation in the earths magnetic field is not necessarily direct although mineral deposits and artificial obof an otherwise uniform field. Generally, however, the natural resources, which may have detectable'or non-detectable influence on the earths field, are genetically or structurally related to certain rock formations which, by their differential magnetic permeabilities, may cause detachable changes in the earths normal field. i

The principles involved in the design of this instrument take account of the fact that the core of the earth acts as a magnet and that the outer shell of the earth is within the magnetic field of that magnet. Any magnetic field is represented in terms of lines of force more or less nearly parallel within small space limits. The field is defined as follows:

First, by determining the angular relationship betwen a line of force and the horizcntal (inclination), second, by the compass bearing of the vertical plane containing the line of force (declination) 3 and third, by

jects may be directly responsible for changes the two poles of the magnet. The normal magnetic field of the earth would be symmetrical with respect to the magnetic polar diameter if it were not distorted by the differences in permeability of the substances which form the earths crust or by the influence of other magnetic fields caused either by natural lodestone or by polarity brought about by either natural or artificial means. All such distortions are included in the changes which our instrument is especially designed to detect.

A small bar magnet mounted at its center of gravity and free to move universally invariably alines itself with the resultant magnetic field, i. e., establishes the space relations of the lines ofl force of that field. At the magnetic equator it would be horizontal, and at the magnetic poles, it would be vertical. The small magnet then, by alining itself with the lines of force of the earths magnetic field, can show changes in direction of said lines of force, but cannot quantitatively show changes in intensity thereof. If, however, the small magnet is brought into a position at right angles to the lines of force of the earths magnetic field, a force will be immediately exerted upon it to malte it aline itself. If the upper pole be given just enough additional inass to hold it at right angles to the lines of force of lthe earths magnetic field at one certain place and the magnet is moved to another place where the force of the earths field is different, then the originally applied mass is no longer exactly compensating and the magnet must change its position. Such a change in position then indicates a change in the magnetic force, and the magnitude of the change in the position of the magnet is an index of the magnitude of the change in intensity ofthe earths field.

Suppose the additional mass originally applied to the magnet to bring it to a position at right angles to. the lines of force of the earths magnetic field remaining constant; if, then, .the magnet is moved to a place where the intensity is the saine but the direction of the field has changed, then the magnet will no longer beV atright angles to the .earthsproximately on line 2-2 of Fig. 1;

Figure 3 isa vertical section on line 3-3 of Fig. 2 looking in thedirection indicated by the arrow; y Y Y Figure 4 is an enlarged longitudinal section V of the swinging assembly-of our improved instrument Figure 5is a vertical section taken approximately on line 5 5 of Fig. 3 and looking inthe direction indicated the arrow',

Figure 6 is an enlarged fragmentary sec- .tional view showing the arrangement for centering the swinging assembly of the instrument transversely of the casing thereof; Figure 7 is a side elevation of the improved mounting forming a part of our invention; Figure 8 is a plan view `of the mounting shown in Fig. 7; Y*

Figure 9 is a section on line 9-9 of Fig. 8; Y Figure 10 is a section detail of one of the adjustable leveling devices ofk our improved mounting;

Figure 11 is a fragmentary detail of onevof theV arms for raising `the swinging assembly 0E of the knife edges. f

Referring now tothe drawings, which illustratethe Vpreferred embodiment of ourv invention, A designates the instrument as a unit. `The instrument'A comprises a casing or housing `liomposed of an annular side wall. 2, a rear wall 8, provided with a sight opening 3 covered by a sheet of transparent inateriai.n and a transparent front wall 4. For the purm pose of 'securing the transparent front wall Y. 4 to the casing or housing 1, we prefer to employ a face ring 5 which is secured to the Vnular sidewall` 2 of the casing or housingby means of screws or other suitable fastening devices 6 (Figs. 1 and 2). The face ring-.5

, is providedV with an inwardly extended flange 5f which provides a shoulder against which said transparent front wall 4 abuts, and 7 designates a guard member, preferably in the form of a split wire ring, which prevents outward movement of the transparent wall 4 with respect to the face ring.

Located within the casing 1 is a scale ring 8; this scale ring is fixed in any convenient manner to the annularside wall 2 ofl the casmoases `ing 1 and extends inwardly therefrom, and

said scale ring is provided with graduations indicating degrees of larc arranged on the face thereof which is located adjacent to the transparent wall 4, as shown clearly in Fia. 1. The scale ring 8, as already stated, is fixed within the casing 1, and 9 designates screws or other suitable fastening devices which are passed through apertures in the rear wall 3 of the casing'and are screwed into tapped openings in the scale ring for the purpose of securing said-rear wall in place on the casing. Arranged at the lower portion of the instru- .ment is a mounting vpost 10 which has associated with it a flange 11, whereby said post is secured to the casing of the instrument, screws or other suitable fastening devices 12 being extended through said flange l1 and being screwed into threaded openings in the annular wall 2 of the casing to accomplish this purpose. The mounting post 10, which is preferably cylindrical in shape and of constant diameter from end to end, is provided with a key 10 the longitudinal axis of which is in the maj or plane of the instrument.

Located within the casing 1 of the instrument at the lower portion thereof and fixed rigidly to the annular side wall 2 at its inner face is a block 13, said block, as shown clearly in Fig. 2, being composed of spaced block portions between which the scale ring 8 passes. Extended upwardly from the respective block portions of the block 13 are bearing supports 14, said bearing supports being secured to the outer faces of the block portions by means of suitable fastening devices 15 so as to provide upstanding arms which are spaced from each other in a direction transverse to the major plane of the instrument. Fixed to the bearing supports by being inserted in recesses at the upper edges 'of members 14 secured to the bearing. supports at the upper ends thereof are bearing members 16 having knife edges attheir upper edges, each bearing support having one of these bearing members associated with it to provide spaced knifee edge bearings. Each of the bearing supports 14 is provided with an open end slot 17a which is located a slight distance downwardly from the top edge of the bearing support and extends inwardly from a side edge thereof, as shown vclearly in Figs. 1 and 3, in which views the portions of the bearing supports 14 which are located above the slots 171 are designated by the reference character 17". As shown clearly in Fig. 6, the portion 17IJ of each of the bearing supports is provided adjacent to theupper edge of the slot 17LL withan inclined face 17C, and also each bearing support is provided at the lower 'edge of the slot 17:L with another inclined members 16 extend a slight distance above the lower edges of the open end slots 172l and are spaced downwardly from the top edges of said slots. l j

Supported by the bearing supports 14 when the instrument is in use the siringing assembly B of our improved instrument, which includes apivot 18 having an annular flange 19 formed thereon. The intermediate portion of the pivot 18 is of greater diameter thanthe remainder thereof, and this intermediate portion is provided with screwthreads 20. The portion 21 of the pivot immediately adjacent to the opposite' ends of the intermediate portion thereof are reduced slightly in diameter, as shown clearly in Fig. 4, and at the extreme opposite ends of the pivot, said pivot is provided with bearing portions 22 which are further reduced in diameter. Also, at the points where the outer bearing portions 22 join the portions 21 of the pivot, said pivot is provided with annular inclined faces 22', as shown in Fig. 6. Screwed on the screwthreaded portion 19 of the pivot is an internally threaded nonmagnetic sleeve 23 having an integrally formed annular' flange 24 Yarranged intermediate of its ends.

Mounted on the sleeve 23 is the magnet 26 of the swinging assembly, said magnet being made of any suitable magnetic material, and may be of laminated construction as shown in the drawing, or of a single thickness of material. The magnet is prefuably shaped as shown in Fig. 1,V but may have other shapes if desired, and is preferably provided with an opening formed through it at its approxivmate center of the approximate diameter of the sleeve 23. The magnet 26 is mounted on the sleeve 23 by having said sleeve passed through the opening at the center of said magnet and said magnet is arranged on the sleeve 23 so that it abuts against the annular flange 24, as shown in Fig. 4. Mounted on the sleeve 23 at an end thereof is a guard ring 25 which is arranged to abut firmly against the portion of the magnet 26 surrounding the opening at the center of said magnet, so that this portion of said magnet is closely confined between the integral flange 24 on the sleeve 23 and the guard ring. After the magnet and guard ring have been arranged in place on the sleeve 23, as described, the end portion of said sleeve adjacent to which the guard ring is located is upset or flared outwardly in any suitable manner, as indicated at 27 in Fig. 4, so that said guard ring is maintained in position on the sleeve. In this connection, it is pointed out that the guard ring 25 is provided with an annular curved face at the opening formed through its center against which the upset portion of the sleeve is caused to closely abut. It is obvious that the portion of the magnet adjacent to the opening at the center thereof is very firmly gripped between the annular flange 24 and the guard ring 25, and, therefore, said magnet will be seceurely xed to said sleeve. 28 designates a spring lock washer which is arranged on the sleeve 23 adjacent to the annular flange 24.

Mounted on the sleeve l23 of the swinging assembly is a counter-arm 29 which comprises an intermediate portion, including a collar portion, at the center thereof, and two arms 30 extended radially from said collar portion. The collar portion of the counterarm 29 is provided with an opening formed therethrough, which is of approximately the diameter of the sleeve 23, and 31 designates a lock nut which is screwed on the screwthreaded portion of the pivot, said lock nut being of such diameter that it overlaps the adjacent end of the sleeve 23 and the collar portion of the counter-arm 29, whereby said sleeve and counter-arm are retained in place on the pivot. Fixed to and extended outwardly from the arms 30 of the counter-arm are counter-arm extensions 32 and 33, said extensions being preferably set into recesses 33 in the outer ends of the arms 30, as shown clearly in Fig. 1, and being fixed in said reces.,Q s in any suitable manner. The extension of the counter-arm has a smooth surface7 but the extension 33 is provided with extremely fine screwthreads which extend from the outer end of the extension to a point thereon which is adjacent to the outer end of the associated arm 30. Mounted on the screwthreaded extension 33 is a counter-weight 34, said counter-weight having an enlarged head portion and an elongated sleeve portion, and, of course, being provided with a threaded opening formed therethrough. It is obvious that the counter-weight may be adjusted longitudinally of the counter-arm extension to change its location thereon by merely screwing the counter-weight lengthwise of said extension, and the reason for this adjustment and its extreme importance will be subsequently pointed out herein. Fixed to the needle 26 adjacent to its opposite ends are arcuate scales 35 formed of non-magnetic material and provided with graduations indicating degrees of are. The positions of the arcuate scales 35 on the needle 26 are such that the outer ends of the counter-arm extensions 32 and 33 are located immediately adjacent to said arcuate scales.

By referring to Fig. 4 of the drawings, it will be obvious that if desired, the counterarm 29 may be moved relative to the needle 2G. The lock nut 31 frictionally engages the collar portion of the counter-arm so that it may not be accidentally moved relative to the needle, but this frictional contact between said elements is not such that it will prevent adjustment of the counter-arm when it is desired to move said counter-arm relative to the needle. lVhen the counter-arm is to be adjusted with respect to the needle 26, the

lOO'

Y proved instrument is in place within the casing,` of the instrument and is in position for use, the opposite reduced end portions 22 of the pivot 18 extend through the Vslots 17a in the bearing supports 14 and rest upon the knife edges at the upper portions of the bearing member 16, and because 'of this arrangement, itis plain that said assembly, if properly leveled, will swing in a vertical plane with the minimun'i friction. However, when the instrument is not in use, as, for instance, when it is being,v transported from place to place, it is desirable that the pivot be removed from' Contact with the knife edges of the bearing member 16 so that these sharp edges will notbe injured. v pair of spaced arms 36 and 36 which are pivoted to the scale ring 8 at the point indicated by the reference character 3'4". f So as tomaintain the arms 36 and 36L in their proper spaced relationship, we form anfopening` in the scale ring 8 the point where the armsBG and 86 are tobe pivotally mounted and extend through `said open:r 0', as shown in Fig. 5, a sleeve 38 which isiixed to saidY scale ringin any suitable manner. A rod 39 is extended through the Ysleeve 38, and this rod is provided atene of its ends with a reducedfportion 40, and at its other end with a screwthreaded opening` 41. At the pivoted end of the arm 36, said arm is provided with an aperture through which the reduced portion 40 ofthe rod 39 extends, said arm being abutted against the shoulder provided at the point where the reduced portion 40 joins the rod39. Mounted on the reduced portion 40 of the rod 39 adjacent to the arm 36 is a lever42 having a hub portion at its approximate center. The reduced port-ion 40 is extended through the `hub portion of the lever 42, and said lever is secured to said reduced portion so that the end portion of the arm 36 willbe closely confined between the hub portion of the lever 42 and the shoulder on the rod 39, whereby the free end of said arm 36 will be caused to swing in an arc of a 4circle when the rod is rot-ated wit-hinthe sleeve 88. in like manner, the arm 36 is seof both of the arms 36 and 36 being raised or lowered depending* on the direction of rotation of said` rod. Arranged on the annular To 'this end, we employ a zii-702,866.5

` side wall of the casing of the instrument is a boss 44 having a screwthreaded opening formed therethrough, and 45 designates a screw which is extended through said screwthreaded openii'n; and is provided with an enlarged head portion to facilitate rotation of said screw. The inner end of the screw 45 contacts with the lever 42 at a point adjacent to one of its ends, and' 46 designates a leaf 'spring which is secured to a suitable bracket 47 fixed within the casing of the instrument, said' leaf spring being adapted to contact with theY opposite end of the lever 42 whereby said leaf spring4 tends to move said lever 42 in a direction opposite to the direction in which Y it is moved by screwing the screw 45 inwardly. y At the free ends of the arms 36 and 3G', said arms are provided with recesses 48 within which the reduced portions 21 of the pivot 18 arelocated. The bottom wall of each of the recesses referred to is more or less V- shaped, as indicated in Fig. 11.

lffhen the instrument is not in use or is being transported, or when, for any other reason, it is desired to raise the pivot from the knife edges of the bearing member 16, the screw 45 may be rotated in a direction to move the inner end thereof outwardly. 'il he result of this will be that the leaf spring' 46 which exerts pressure against the lower end ofthe lever 42 will move said lower' end of said lever inwardly about the pivot 37 of said lever, whereby the upper end of the level' 42 will move outwardly with the inner end of the screw 45, and, therefore, the free ends of the arms 36 and 36 will be moved upwardly in an arc. of a circle drawn from the center of the sleeve 38. As the free ends of the arms moveupwardly as described, the pivot will be picked up by the bottom walls of the recesses 4S in said arms, whereby said pivot will be moved oft of the knife edges of the members 16. y The pivot will then rest in the lowermost port-ion of the V-shaped bottom walls of the recesses and a continued movement of thefree ends of the arms 36 and 36 in an upward direction will cause said pivot to be clan'iped between the bottom walls of the recesses in the arms and the portions 17" of the bearing supports 14 (Fig. 2).

It is obvious, of course, that when it is desired to replace the pivot on the knife edges of the bearin members 16, it will be necessary to merely rotate the screw 45 in a direction to causeits inner end to move inwardly, whereby the lever will be moved in a direction to cause the free ends of the arms 36 and 36 to be moved downwardly. The V-shaped bottom walls of the recesses 48 in the arms 36 and 36 function as centering `devices for the pivot inasmuch as `the inclined port-ions of said bottom walls will cause saidv pivot to moveto the lowermost points thereof, which areV at the centers of said bottom walls, and, therefore, the pivot portions 22 will be placed in contact with the same portions of the knife edges each time said pivot portions are operation when the pivot 18 is raised from the knife edges by the arms 36 and 36. If,

when the pivot 18 is raised by the arms 36 and 36', said pivot is out of its proper lateral position within the casing, one or the other annular inclined faces 22 will engage the fassociated inclined face 17C on one of the bea-ring supports 14. The result of this will be that the pivot will be shifted laterally to its proper lateral position. The means for centering the pivot so that it is always caused Y to contact with the same portions of the knife edges (the V-shaped bottom walls of the recesses 48 at the outer ends of the arms 36 and 36) and the means for shifting the pivot transversely of the casing so as to cause the same portions of the pivot to contact with the knife edges every time said pivot is lowered onto the knife edges (the inclined faces 17c on the bearing supports 14 and the annular inclined faces 22 on the pivot) are eX- tremely important features of our invention in that they cause the same portions of the pivot and the same portions of the knife edges to be in contact every time a reading of the instrument is being taken. The extreme importance of this results from the 'fact that the portions V22 of the pivot and the I knife edges may not be absolutely uniform throughout. These parts are madelwitli thel hence the accuracy of the instrumentwould be affected. VIn the use of ourimproved instrument, however, the pivot 18 is centered every time it is raised from the knife edges and as a result of this the same portions of the pivot will contact with the same portions of the knife edges every time the pivot is lowered onto the knife edges, whereby a uniformity of conditions at the pivot points of the swinging assembly will result.

Since temperature changes cause changes in the position of the magnet comparable to those caused by changes in the magnetic field, itis absolutely essential to correct for the effect of temperature changes. To do this, we employ aI thermometer 50 which is installed within the casing of the instrument, said thermometer being secured in place by suitable brackets 51, preferably to the rear wall of the casing of the instrument. In this connection also, we propose, if it is found to be necessary or desirable, to eliminate the effect of temperature changes'on the counterarm by making the extensions 82 and 33 of said counter-arm of materials having 'different coeflicients of expansion. Because of this arrangement, the expansion of one counterarm extension will be compensated by the other extension.

The instrument as a unit is provided wit-h a leveling' device 52, preferably of the bubble type, which is secured within the casing of the instrument, whereby said instrument may be properly level. The leveling device 52 is arranged exactly parallel with the klnife l edge of each of the members 16 and its function is to aid iii determining the horizontalityV of the individual knife edges, it being plain, because of the parallel arrangement of the leveling device and the members 16, that the knife edges of the members 16 will be horizontal when the bubble of the leveling device sliows that said leveling device is horizontal. This leveling device, howevei', will not assist in determining whether or not the associated knife edges are in the same horizontal plane with respect to each other, this function being performed by other leveling devices which will be subsequently set forth herein. Due to the transparent front wall 4, the sight opening the cut-out portions 1"('5L in the pivot guides 17, the user of the instrument may see the knife edges and pivot 18 at the points where they contact with each other when the instrument is in use.

In the use of our improved instrument,

each time a reading is to be taken it is advisi able to bring the swinging assembly B to a cert-ain position with respect to the scale ring and permit said assembly to swing from that point, To provide for moving the swinging assembly to this certain position, we employ a mechanism which is clearly shown in Fig. 2 and which comprises a rod V.'55 supported for longitudinal and rotary movement within a sleeve 56 fixed in an opening formedin the rear wall of the casing. The rod 55 is provided at .its outer end with a knurled head 5'? and 58 des- 57 and the outer end of the sleeve 56, respecr tively, said coil spring tending to move the rod 55 outwardly. 59 designates an .arm which is secured to the rod 55 at the inner end thereof, said arm being. provided with .a laterally extended portion 60.

in the rear wall 3 and l y Aio -When it is desir-edito set the swinging assembly to any particular point on the ring scale, the rod' 55 willbe moved inwardly by pressing'on thehead 57. yThis .will cause the portion 60 of the arm 57 to overlapthel path "oftravel of theineedlef26 of the swinging assembly and'if the rod is then rotated by lturning the head 57, the needle 26 will be picked up by the rotating portion 60 of thearm 59 and said needle, together with the associated parts, comprising the swinging assembly, will be moved to the desired position. lt is obvious, of course, that when the inwardk pressure on the rod 55 is relieved, the coil spring 58: vwill move the rod out-wardlyk and, of course,

when said rod Vis in its Voutermost position, as

shown in Fig. 2, the portion 60 of the arm 59` will-.be outofv thefvpath of travel of the needle Because of its const friction, itfhas beenV found that our improved instrument will not function in -V an Ventirely successful manner when supported` on the `ordinary tripod mounting, and we have, therefore, devised a special mounting which willnow be desciibed.

Referring now to Figs. 7, 8, 9 and l0 of the drawings, C designates our improved mount-l ing, which comprises a tripod head 65 to which thelegs66 of the mounting are pivotally secured in the usual manner, which ordinarily includes bolts 67 provided with wingnuts 68.

is a member 69 having an upwardly extended screwthreaded portion 70 (Fig. 9). 7l desig- .nates the leveling head platform of 'our improved mounting which is provided withv an annular downwardly extended portion 72 pro- Y, terior of 4said portion-78 kproi'fiding a socket i forth.

75which is for arpurpose to be hereinafter set 76 designatesrthe meunting socket vof our improved mounting which comprises an elon- 1 gated tubehaving external Vscrewthreadsat its lower end. The longitudinal opening through the tube`76 is provided with a portion of enlarged diameter'adj acent tothe lupper end of said tube-as indicated by the reference character 77, Vand they wall vof the tube is provided with a slot 78 which extends downwardly Y from the-'topedge of the tube, at which top edge of said tube said slot 7 8 is open. The

"i elongated tube7 6 is provided at its upper end with a reduced portion 8OV at the lower end of which a shoulder 8l is arranged, as shownclearly in Fig. 9. lMounted on the elongated tubey Gat thereduced upper portion thereof is a 'split collar 82 provided with a4 pair of integrally formed spaced ears 83 which extend outwardly from the elongated tubeat the opposite sides of the slot 8l. The split collar 82 contacts with the shoulder 81 on the elongated tube and said split collar is fixed to said elongated tube so that the space between the ears 83 of said split collar is in alignment with the slot 7 8 at the upper end of the elongated tube by means of a screw 82 which passes through said split collar and into an aperture in the tube 76. Extended through screwthreaded apertures in the ears 88 is a clamping screw 84 providedn'ith radial pins 84 whiclifacilitate rotation of said screw. The portion 85 of the clamping screw which is provided with screwthreads is reduced in diameter and a shoulder 86 is provided where this reduced portion joins lthe remainder of Ysaid clamping screw. The tube. 76 is formed of material possessed of some resiliency, and it is obvious, therefore, when the shoulder 86 is brought into contact with a face of one of the ears 83 andthe clamping screw is rotated in the proper direction, the ears 83 will be drawn toward each other, whereby the `upper portionV of the tube V7 6 will be contracted slightly, thus providing for grippingl an element which may beext'ended into the enlarged upper portion of the opening, formed through l the tube. Mounted on and fixed. to the tripod -liead The lower portion of the tube 7 6 is extendthe upwardly extended portion 78 of the leveling head platform, and located within the fsocket75 provided by said portion 78, and 87 designates a collar which is mounted on the tube 76 by being screwed on the screwthreadyed lower end thereof so that said collar is positioned within sa-id socketr'. The collar 87 is provided with a curved face`r 87 which is llocated adjacent toa correspondingly curved face 75 within the socket 5, whereby a universal jointbetween the leveling head platform and the mounting socket is provided.

Fixed on the elongated tube 76 at a. point intermediate its upper and lower ends is the leveling head-88 of our improved mounting,

whichwhen viewed in plan, is preferably shaped as shown in Fig. 8. The leveling head may be formed integral with the tube 76 or may be separable and fixed thereto as desired.

rand said head is provided with a plurality of screwthreaded apertures 89 formed therethrough. 9()V designates plurality of leveling screws by means of which the leveling head may be adjusted as to horizontality. Each of the leveling screws comprises screw- Ythreaded portionQl which is passed through one of the threaded apertures in the leveling head, an enlarged portion 92 to .facilitate manipulation of the screws and a spherical lower portion 93 adapted to extend into a suitably shaped seat in a shoe 94., which contacts with the top face of the leveling platform 8l.

als

ed through the aperture 7 l in the top wall of iio The shoes 94 are secured to the spherical lower ends of theleveling screws by drawing the metal of the shoe about the curved upperl portion of said spherical portions.

Mounted on the leveling head 88 is a pair et leveling devices 95 and 90, preferably of the bubble type, said leveling devices being arranged at right angles with respect to each other, as shown clearly in Fig. 8. Each oit the leveling devices includes an elongated bar 97 to which the tubular portion of the level proper is secured in any suitable manner, and 98 designates bars which are secured to the leveling head for the purpose of supporting the leveling devices. The bars 98 are fixed to the leveling head in any suitable manner and said bas are of approximately the same dimensions as the bars 97 Jforming parts of the leveling devices, the last mentioned Abars being arranged immediately above the bars 98 with a slight space therebetween, as shown clearly in Fig. 10. Inter-posed between each pair of associated bars 97 and 98 is a leaf spring 99 which is curved so that it tends to separate said bars. The leaf springs 99 are each provided with elongated apertures 100 acent to the opposite ends thereot, and 101 designates screws which pass through openings at the opposite ends ot the bars 97 and 98l and through the elongated apertures 100 in the leaf springs 99. The openings in the bars 98 through which the screws 101 pass are screwthreaded and the enlarged head portions ot said screws 101 H contact with the .top faces of the bars 97 whereby said bars 97 may be adjusted relative to the associated bars 98 by manipulating the screws 101. Y

The lirst step necessary in preparing for the use et' our improved instrument is to determine the direction of the vertical plane of the magnetic meridian, as our improved instrument is to be set in that plane. This plane is determined by a magnetic compass (not shown) which isprovided with a mounting post resembling the mounting post 10 of our instrument, the mounting post ot the compass being of such length and diameterthat it will lit into the upper portion of the (mening formed through the mounting socket ot the mounting C and being provided with a rey resembling the key 10 of the instrument pest 10. The mounting post of the compass extended into the opening in the mounting soclretof the mounting and the key is arranged within the open-end slot 78 in the tube 7G, after which the mounting post `oi the compass is clamped in the upper end of the mounting .Socket by tightening the clamping screw 84,V The mounting is then turned if necessary until the transverse dimension of the slot 78 is parallel with. the magnetic meridian as determined .by the needle of the compass.

When the mounting has been set as described, the clamping screw 8i will be unscrewed andthe comjass will be removed from the mounting, after which our instrument will be mounted on the tripod by introducing the mounting post l0 into the opening 'in the mounting soclret and with the key 10 in the slot- 7 8. after which said mounting post will be firmly clamped in place by tightening the clamping screw Due to the fact that the key 10 is in the majer vertical plane oi1 the instrument and as said ley is located in the slot 78, which is arranged in the directicn of the nu plain when our instrument has been mounted on the tripod as described Vthat said instrument will be in the plane of the magnetic meridian. Then the instrument has been mounted on the tripod, the istruinent will be leveled by manipulatin the leveling screws 90, this operation being aided by reference to the bubble levels 95 and 96 on the leveling head 88 and the bubble level within the instrument. The pivot then lowered into contact with the knife edges ot the bearing members 16 and the swinging assembly is permitted to swing. The operator will watch the pivot and the knife edges very closely during the swinging ot the assembly B, the opposite ends of the pivot being visible through the front transparent wall of the casing` and through the sight opening 3 in the rear wall ot said casing, in order to determine whether any portion ot the pivot is i-mjiinging against the knife edges or bearin supports 14. for it the pivot does so iinpinge it indicates that-one oi the lfcnife edges is in a lower horizontalV plane than the associated knife edge, which. causes the pivot to creep laterally ot' thecasin as the assenjibly swings. In the event the pivot impinges against the lrnite edges of the bearing supports 11i, the leveling head will be adjusted by manipulating certain ot the leveling screws until it has been` determined that the swinging assembly swings freely* The adjustable level bubble arran 'ed transversely oi the plane of the instrument then properly adjusted.

The next step is to determii'ie the direction Ot the lines et torce of the earths magnetic ield which is done by removing the counterweight and arranging the counter-arm so that it is parallel with the axis oit the needle 2G. The swinging` assembly will then aline its magret with the direction oit the lines ol? force oit the magnetic iicld an d the ot inclination ot these lines ot torce may be. had

by referring to the ring scale 8. The angle between the extensions oit the counter-arm and the artis of the needle if@ determines the sensitivity of the insti, ment and the counter-.arm is neeztadj usted to the desired angle, after the counter-weight 8d has been applied to the counter-arm extension 83. The counter-weight is adjusted to a position on the counter-arm which will cause the needle to `v'netic i eridian, it is lili) come to rest approximately at right angles to the inclination'of the lines of force'of thel earths magnetic field, the arcuate scales beine' utilized for fixing the propcivangle between the counter-arm and the needle. The* angle between the counter-arm and the axis of the needle is determined after the angle lof inclination of` the earths field has been fixed ivith reference to the horizontal and the Y complet to this angle becomes the mai-:iinum limit for the to be set olf ou the arcuate scales. ln this connection, if the maximum sensitivity is desired, the angle set off on. the arcuate scales should depart from Athe maximum limit only by that amount which is ameasure of the friction. This adjustment requires set` and try 'proceduie.

lifter the adjustments With respect to the angle-between the counter-arm and the needle Vhav'e been made and the counter-Weight has been properlyl positioned on the counter-arm,

the temperature coefficient is determined and v,the instrument is'ready for a reading.V

'lo take a reading, the swinging assembly of the instrument is brought to a certain position With respect to the ring scale,`pre fer ably Vthe zero position, by movingl the rod extended through the rear wall of the instru- Vnient inwardly so that the portion GO of the arm 59 ned to said rodivill contact With the needle 26 of the swinging assembly, whereby Vrotary moven'ient of the rod 55 will move the needle to the desired position. When the swinging assembly has been broughtto its starting position, and this position Will be thc'same each time a reading` is taken, the

portion 60 of the-arm 59 will be moved out of theA )ath of travel of the needle 26 and the svf Qing assembly willy be permitted to wiring, the initial position of the needle and he end of the swing being recorded. The

.fined in order that the-momentum ofthe Contact between the knife edges ofthe members i6 and the pivot. y n

ln levelingour improved instrument preparatory to taking a reading, We have found that Wind pressure'may move the instrument out of its proper position so that the knifeedgge bearings, which in the absence of Wind pressure would be in exactly the same horiiiieresult of this Would be that the .ot of the swinging assembly would creep traiisvcrsely'oi` ie casingV of the instrument and would iniping'e affains't the knife-edge be members or against the bearing` Vsupports le. lo avoid this condition, We provide the instrument mounting with the leveldevices 9 5 and 96,already referred to, whichmay beV adjusted. relative to the leveling head. ln the eventv our instrument has been set up and leveled and Wind pressure against theinstruinent moves the instrument Y assembly is caused to swing as de- -wingij iiray overcome friction inherent in the zontal plane, ivillbe in different horizontal out of its true position so that the knife edges are not in the same horizontal plane, the operator will manipulate the levcling'screivs associated with the leveling head of the tripod until tests made by permitting the swinging assembly to svviiigi` show that the knife edges are iii exactly the saine horizontal plane. This manipulation, of course, will throw the levels 95 and'QG out of their leveled positions, and, therefore, when the instrument is moved from one location to another, the operator will not be able to deterniiiie the exact setting of the instrument at the previous location.l

life have, therefore, arranged the levels 95 96 so that they are adjustable with respect to the levelinghead of the tripod. Hence, When the instrument has been adjusted for ivind pressure as described and the vlevels 95 and 96 moved from their leveled Aof gravity andthe magnetic :lield are equal and opposite in'theirv Aeffect on the needle. Hence, the slightest change in the magnetic force, either increase or decrease, results iii ,changing the position of the needle. It is obvious that the only bar to infinite sensitivity in the instrument is the lack of mechanical perfection in its making, and it is likewise plain that any ldegree of sensitivity desiree may be obtained by varying` the angle between the counter-arm and the long' axis of the needle.y Field work has proved that `this instrument may be adj usted so that it can be made to react to changes in the earths Y magnetic field with a sensitivity of the order of magnitude of twenty times the sensitivity shown by the average ordinary dip needle.

Up to this point ive have stressed particularly changes in field intensity and the sensitivity of our instrument thereto. TWe can novv demonstrate that the combination ofthe counter-arm 29, adjustable to any angle desired Which Will be indicated on the arcuate scales 35, and the adjustable counter-Weight 3e borne by the counter-arm 29, by means of all of Which We control thescnsitivity of the swinging magnet to minute changes of iiitensity, has been so designed that the instrument adapts itself to minor changes in inclination in Asuoli a manner that Wherever .maximum sensitivity is most desired the sensitivity Will automatically approach theoreti- Y cal infinity and depart therefrom by an amount limited only by coiistiuctional detail influencing friction.

the changed intensity.v Y

Intensity changes are always accompanied byv greater or less changes of declination and inclination, as defined by lines of force. Then the instrument is adjusted in the manner previously described herein and with thc counter-arm 29 setting olf on the arcuate scale an angle approximating the complement of the angle of regional inclination and depart-ing therefrom by no less than an amount representing effective friction, and with the counter-weight 34 so placed that the swinging magnet indicates its position of rest to be at right'angles to the lines of force in the plane of the magnetic meridian, then wherever the inclination and intensity of the field have ident-ical values the magnet will register this same position. However, where different values are encountered at succeeding stations, since `inclination has changed, sensitivity to intensity also has changed. If the angle set off on the arcuate scales 35 be less than the amount affording infinite sensitivity to changes of intensity at the given inclination, and if the inclination steepens by such an angle that the angle set off on the arcuate scales 85 becomes the complement of the steepened inclination, then the instrument becomes automatically possessed of theoretical infinite sensitivity to By reason of this feature in the design of the instrument, when it is used for reconnaissance, those adjustments made for maximumY practical sensitivity to intensity changes in the regional inclination. automatically adapt themselves to higher sensitivity wherever local distortions have steepened the regional inclination. Thus, the instrument automaticallyattains its optimum of' working sensitivity whenever it encounters the actual conditions it is designed to detect. For extremely refined detail, the adjustments can be so arranged as to yield theoretically infinite sensitivity in strategic locations. p

While we have shown in the drawings and described in the specification one embodiment of our invention, we do not wish to be limited to the precise construction disclosed nor to any specific materials, as' it is obvious that the invention ccmprehends changes, variations and modiications which come within the scope of the claims hereunto appended.

The instrument mountingl shown, but not claimed in this application is claimed in an application filed in the name of Noel H. Stearn on December 31st, 1928, which application bears Serial Number 329,599.

We claim:

1. An instrument comprising a magnet mounted to swing in a vertical plane, a counter-arm movable with said magnet and angularly adjustable with respect thereto, and means for indicating the degree of angularity between said magnet and said counterarm. y

2. An instrument comprising a magnet mounted to in a vertical plane, a counter-arm movable with said magnet and angularly adjustable with respectthereto, and means ixed to said magnet for indicating the degree of angularity between said magnet and said counter-arm.

3. An instrument comprising a magnet mounted at its approximate longitudinal center so as to swing in a vertical plane, and a counter-arm mounted intermediate of its ends at a point in horizontal alinment with the point of support of said magnet, said counter-arm being` movable with said magnet and being angularly adjustable with respect thereto.

4. An instrument comprising a magnet mounted to swing in a vertical plane, a pivot by which said magnet is supported, supports for said pivot, and a counter-arm supported intermediate of its ends by said pivot, said magnet, said pivot, and said counter-arm being movable as a unit and said counter-arm being angularly adjustable with respect to said magnet.

` 5. An instrument comprising a magnet mounted to swing in a vertical plane, a pivot by whichsaid magnet is supported, supports for said pivot, a counter-arm supported intermediate of its ends by said pivot, said magnet,

said pivot and said counter-arm being movableias a unit and said counter-arm being adj ustable with respect to said magnet, and friction meansfor preventing accidental movement of said counter-arm with respect to said magnet. Y

6. An instrument comprising a magnet mounted to swing in a vertical plane, a counter-arm movable with said magnet and angularly adjustable with respect thereto, and a counter-weight mounted on said counter-armV and adjustable thereon.

7. An instrument comprising a magnet mounted to swing in a vertical plane, a screwthreaded counter-arm movable with said magnet and angularly adjustable with respect thereto, and a screwthreaded longitudinally adjustable counter-weight on said screwthreaded counter-arm.

8. An instrument comprising a magnet mounted to swing in a vertical plane, a pivot by which said magnet is supported, supports for said magnet on which said pivot rests, and means whereby said pivot may be adjusted longitudinally of its major axis with respect to said supports.

9. An instrument comprising a magnet mounted to swing in a vertical plane, a pivot by which said magnet is supported, supports for said pivot, a screwthreaded counter-arm supported intermediate of its ends by said pivot, said magnet, said pivot, and said councal portions ofsaid pivot are adapted to rest.4

vided with corresponding inclined faces located inver-tical alinement with respect to the inclined faces on ysaid pivot, and means for moving said pivot off of said supports by rais-y ing same therefrom. Y

11. An instrument comprising a magnet mounted to swing in a vertical plane, a pivot Vby which said magnet is supported, supports n for said pivot on which said pivot rests, means whereby said pivot may be moved oif of said supports, said means including an arm piv oted` to a fixed part of the instrument andarra-nged to contact with said pivot and move saineupwardly,`aiid lia-ving an inclined face with which said pivot may contact.

12. An instrument comprising a magnet mounted to swing in a vertical-plane,.a vpivot having cylindrical portions by which said magnet is supported, supports for saidy pivot Y on which said pivot restameans whereby said pivot may be moved off of said supports by being raised therefrom, said means including spaced arms provided with recesses khaving inclined faces therein in which the oylindri- 13. An Vinstrument lcomprising a magnet mounted to swing ina vertical plane7 a pivot' having `vcylindrical portions by which said magnet is supported, supports'for said pivot on Which said pivot rests, means whereby said pivot may be moved ed of said supports by being raisedtherefrom, said lmea-ns including spaced arms provided with recesses having convergent inclined faces therein in which thc cylindricalportioiis of said pivot are adapted to rest.

14;. An instrument comprising a. magnet mounted to swing in a vertical plane, a pivot by which said magnet is supported, supports for said pivot, means having inclined faces whereby said pivot may be shifted longitudinally of its major axis, and means including an arm provided with an inclined face whereby said pivot may be shifted at an angle to its major axis.

l5. An instrument coiiipi'isiiig a magnet mounted to swing iii a vertical piane, a pivot by which said magnet is suj'iported, said pivot being provided with inclined faces, supports for said pivot, said supports being provided with inclined faces, means whereby said pivot may be moved o of said supports by being raised therefrom, to move the inclined faces on said pivot into contact with the inclined faces on said supports, said means for elevating said pivot including spaced arms provided with recesses having inclined faces arranged therein within which portions of said pivot are extended.

16.V An instrument comprising a magnet mounted to swing iii a vertical plane, a Counter-arm movable with said magnetand angularly adjustable with respect thereto, la pivot by'which said magnety is supported, supports for said pivot, means for moving said pivot off of said supports, means for adjusting said pivot longitudinally of its major airis with respect to saidsupports, and means associated with the means fornioving said pivot off of said supports for adjusting said pivot at an angle with respect to its major axis.

1n testimony whereof, we have hereunto set our hands.

- VILLIAM O. HOTGHKISS.

HENRY R. ALDRlCH. NOEL. H. STEA-RN.

JOHN P. FOERST. 

